An innovative process for lead upgrade from Kaldo smelting slag of lead ores: characterization and flotation

This study aims to float lead from the lead smelting slag of a Kaldo furnace. The slag characterization showed that the slag consisted of galena, quartz, metallic lead, sphalerite, and pyrrhotite (10.3% Pb, 5.1% Zn, and 20% Fe). Flotation experiments were conducted on the slag using potassium amyl xanthate (PAX), zinc sulfate, and sodium cyanide. Increasing the concentration of PAX improved lead recovery due to the oxidation of the xanthate ion. Due to the particles engaged, zinc sulfate and sodium cyanide were not effective in depressing zinc and iron, and often resulted in the depression of lead. Under optimal conditions of 800 g/ton PAX, 250 g/ton zinc sulfate, and 50 g/ton sodium cyanide at a pH of 9.5, a lead concentrate containing 21.5% lead with a recovery of 61.17% was obtained, alongside zinc and iron recoveries of 45.34% and 26.76%, respectively. Given the 1200 °C operating temperature of the Kaldo furnace and the melting points of lead, zinc, and iron, lead and zinc are more susceptible to changes in physical and chemical properties and to form an alloy. This is a significant factor contributing to high zinc recovery in lead concentrate.